Ask most runners how a session went and they’ll tell you their pace. Ask them how it felt and they’ll shrug. That’s backwards. Pace is an output – it tells you what happened. RPE (Rate of Perceived Exertion) tells you what it cost to produce that output, and cost is the number that actually predicts whether you’re adapting well or heading toward a wall. It’s my primary training metric in my own marathon build, not just something I hand runners on paper.
The scale
RPE runs 0–10. This is the version I use with the runners I coach:
| RPE | Session type |
|---|---|
| 0 | Day off |
| 1 | Recovery jog, no stress |
| 2–3 | Easy runs, full conversational pace |
| 4 | Steady long run or a short, sharp hill session |
| 5 | Quality long run, track speed work, or a moderate hill session |
| 6 | Threshold efforts (10–20 min) or a progressive long run |
| 7 | Track intervals, 3–5 min efforts, hard long run |
| 8 | Hard hill or hard track session |
| 9 | 3–10km time trial effort |
| 10 | Race-day max, PB attempt |
That’s the reference table. The part that actually matters is what to do with it.
Why pace and heart rate aren’t enough on their own
Pace is context-dependent – heat, wind, terrain, and fatigue all change what a given pace costs you on a given day. Heart rate is more honest, but it lags effort by design and drifts upward across a session even at constant output, especially in heat or with accumulated fatigue. Neither tells you, in real time, how hard the effort actually feels to produce.
RPE is the only one of the three that responds instantly to everything affecting you that day – sleep, stress, heat, prior training load. That’s not a weakness, it’s the point. A 5/10 effort that produces a slower pace than last week isn’t a bad session. It’s your body telling you accurately what today cost. Runners who chase last week’s pace regardless of how it feels are the ones who turn a normal down day into an overreaching week.
Correcting a common misunderstanding
You’ll see RPE zones described as “lactic acid processing” zones. That’s outdated language and it undersells what’s actually happening. What changes across the RPE spectrum is your relationship to two physiological markers: the point where lactate starts accumulating faster than it can be cleared (roughly RPE 4–5 territory for most trained runners), and the point where that accumulation becomes unsustainable for more than a short period (roughly RPE 6–7). Below the first marker, you’re building aerobic capacity and mitochondrial density with minimal fatigue cost. Between the two, you’re training your ability to clear lactate at a higher output – the “threshold” zone. Above the second, you’re training tolerance to accumulating fatigue, which has a real cost and a real ceiling on how often it should be repeated in a week.
This is why RPE and physiological zones should agree most of the time – if your RPE 6 threshold effort has you at what should be an RPE 8 heart rate, that’s a signal (fatigue, heat, illness building), not something to push through.
Where RPE matters most: injury-prone and masters runners
If you’ve got an injury history, RPE is your best early-warning system. A day where your usual easy pace suddenly feels like a 4 instead of a 2 is data – it’s telling you something is off before it shows up as pain. Training strictly by pace ignores that signal completely; training by RPE catches it in real time.
For masters runners specifically, recovery capacity changes with age in ways that a fixed pace target doesn’t account for. The same session that was a 5/10 two years ago might legitimately be a 6/10 now at the identical pace, and that’s not decline you need to fight – it’s information about how much recovery that session now requires. Runners who keep training by yesterday’s pace targets, ignoring what today’s RPE is telling them, are the ones who accumulate the kind of chronic fatigue that turns into an overuse injury.
Using RPE inside a structured block
Inside a load week, your RPE should track with the session’s intended zone – if it doesn’t, that’s useful information about whether the block needs adjusting, not something to override by pushing to hit a number. Inside a deload week, RPE should sit noticeably lower across the board even at similar paces; if it doesn’t, the deload isn’t doing its job and something in the load block needs a second look.
RPE isn’t a soft, secondary metric you fall back on when you don’t have a watch. Used properly, it’s the fastest and most accurate read you have on how your training is actually landing – and it’s free.
The log tells you the pattern. Working out what to actually do about a pattern that keeps repeating – that’s the part most runners get stuck on alone, and it’s the part I help with once we’re looking at a few weeks of your own data together.
